The present invention relates to a system for driving an ink drop generator of an ink-jet printer.
In the prior art ink drop generators, the pressure in an ink manifold is made negative so as to aspirate the ink so that the ink manifold also tends to aspirate the air through an ink issuing nozzle. In practice, however, because of the surface tension of the ink and the capillary action in the nozzle, the suction of the air into the manifold is prevented. However as the ink drop frequency is increased, the ink must be replenished within a very short time, the volume of replenished ink being equal to the volume of an ink drop issued. As a result the pressure in the ink manifold becomes more negative so that the air is also sucked through the nozzle.
Furthermore in the prior art multi-nozzle ink drop generators, a common piezoelectric element is generally used so that the pressure waves are dispersed and consequently not concentrated on each nozzle. As a result, the ink drop issuing efficiency is low.
There has been invented and demonstrated an ink drop generator of the type provided with two piezoelectric elements so as to impart mechanical excitation to two ink chambers in an ink manifold. However, because of the angular displacement between the two piezoelectric elements, the pressure waves are out of phase and the volumes of ink issued from the two chambers are different. As a result, the point at which the ink jet breaks into ink drops varies and the resulting ink drops are varied in size.